Historically, writing instruments such as pens and pencils have been manufactured where the caps and/or barrels have various colors and designs on them. These different colors and designs are typically painted or printed on the pens and pencils.
Another type of instrument available in the industry is a "wrapped" writing instrument. Wrapped pens and pencils include patterns that create interesting optical and illusionary effects. These wraps are sometimes called foil wraps because the pens and pencils are actually wrapped in printed foil.
Recently, thermochromic writing instruments have become available on a very limited basis. The term thermochromic generally refers to the chemical property of changing color based on heat. Thermochromic pens and pencils change color based on the application of heat to the pen or pencil, e.g. the heat from one's hand. Thermochromic writing instruments may be manufactured in two ways: (1) with a thermochromic coating topically applied to the pens and pencils; or (2) by injection molding, with thermochromic pigments dispersed in the plastic prior to injecting.
Applicant is aware of only two companies that offer thermochromic writing instruments. They are Bic Corporation, which manufactures injection-molded thermochromic pens, and Calladium Corporation, the Applicant, which offers thermochromic writing instruments manufactured with coatings. The injection molding method may be used only with pens, while the coating method may be used to manufacture pens and pencils.
Different materials may be used to manufacture thermochromic writing instruments having topically applied coatings. For example, the writing instruments may be coated with thermochromic pigments dispersed in a lacquer base, as described more fully in a patent application entitled "Method for Making Thermochromic Writing Instruments Using Topically Applied Thermochromic Pigments," application Ser. No. 08/519,918 filed on Aug. 28, 1995. Alternatively, the writing instruments may be coated with liquid crystals and various protective lacquers, as described more fully in a patent application entitled "Method for Making Liquid Crystal-Coated Thermochromic Writing Instruments," application Ser. No. 08/673,146 filed on Jul. 1, 1996.
While the above-described prior art writing instruments have merit, there are disadvantages associated with each. This is true for the non-color changing writing instruments. Children often become bored with "plain" pens and pencils that can't "do" anything. Similarly, foil-wrapped pens and pencils are less appealing than interactive, thermochromic writing instruments.
Color-changing prior art writing instruments also have disadvantages. Thermochromic writing instruments made with injection molding are very slow to respond to the application of heat, and can only change two colors. An injection-molded thermochromic pen might require in excess of forty-five (45) seconds to react to the holder's body heat and change color. In addition, due to the injection molding manufacturing process, the thermochromic pigment must be microencapsulated with thick walls. The thick walls further retard the ability of the writing instrument to change the pigment color in response to applied heat. In addition, the pens manufactured with an injection molding process often have a dull or muted color that is less appealing to children.
While topically applied, thermochromic pigment-containing writing instruments change color faster than injection-molded thermochromic writing instruments, topically applied thermochromic writing instruments are not as responsive as desired. In addition, the topically applied thermochromic pigments are only capable of changing between two chemical states (i.e., active and inactive), thus providing only two distinct colors.
In addition, the surface of prior art writing instruments may be scratched during use. This scratching affects the appearance of the writing instrument and decreases the ability of the writing instrument to change color when heat is applied to the writing instrument.
Finally, purchasers of writing instruments constantly seek new, different writing instruments from those presently available on the market. Thus, there is a need for a method for making thermochromic writing instruments that rapidly change color in response to heat application and have a different appearance and/or texture than prior art writing instruments.